Copper is essential for normal human metabolism. Inborn defects in function of proteins distributing copper within the body lead to severe metabolic disorders, such as Menkes disease and Wilson disease, which are characterized by neurological and hepatic abnormalities, renal and vascular damage. The copper transporting ATPases, ATP7A (Menkes disease protein) and ATP7B (Wilson disease protein), have been identified as key regulators of copper concentration in human cells. In recent years, information on biochemical and intracellular properties of these transporters has been rapidly generated. However, little is known about the distinct physiological roles of ATP7A and ATP7B. Our long term goal is to characterize specific roles of ATP7A and ATP7B in copper homeostasis as a prerequisite to the development and improvement of therapeutic treatments for these disorders. The major goal of this proposal is to understand specific roles of ATP7A and ATP7B in copper transport. Using recombinant protein construction, site directed mutagenesis, segment exchanging experiments, and copper binding affinity assays;we will determine the role of a unique sequence insert in the function and trafficking of ATP7A and ATP7B. Also, we will investigate the role of acceptor proteins on copper release by measuring the rate of copper transport of ATP7A after overexpression or knock-down of peptidyl-a-monooxygenase. Finally, we will examine the dependence of ATP7B activity on CIC-4, a mammalian endosomal CI-/H+ exchanger with poorly understood function in cell physiology. The result of the proposed research will yield information essential for understanding and better treatment of Menkes disease and Wilson disease. PUBLIC HEALTH RELEVANCE: Menkes disease and Wilson disease are characterized by neurological and hepatic abnormalities, renal and vascular damage, and are caused by a disruption in function of the enzymes ATP7A and ATP7B, respectively. Our goal is to characterize the specific roles of ATP7A and ATP7B as a prerequisite to the development and improvement of therapeutic treatments for these disorders.